<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <link rel="stylesheet" href="16.css">
    <title>CSS值与单位</title>
    </head> 
    <body>
        <h1>CSS值与单位</h1>
        <ul class="ems">
            <li>选项1</li>
            <li>选项2</li>
            <li>选项3</li>
        </ul>
            <ul>
                <li>子选项1</li>
                <li>子选项2</li> 
            </ul>
            <p class="color_demo">颜色值</p>
        <div class="box bg-image"></div>
        <div class="box bg-gradient"></div>
    </body>
</html>